The field of this invention relates to a networked system of pyrotechnic devices.
Pyrotechnic devices play an increasingly important role in aerospace vehicles and systems such as rockets, aircraft and spacecraft. As an example, the number of pyrotechnic devices used on a typical missile has increased over the years from less than ten to as many as two hundred or more. The additional pyrotechnic devices may be used for several purposes. For example, multiple lower-powered initiators may be used in place of a single higher-powered initiator to provide flexibility in the amount of force that can be generated at a single location on the vehicle. However, the use of additional pyrotechnic devices carries with it the burden of additional infrastructure within the vehicle or system using these devices. As the number of pyrotechnic devices in a vehicle or system increases, several other things increase as well, such as cabling length, cable quantity, weight, number of parts, power usage, system complexity, manufacturing time and system cost. In an environment such as a rocket or missile, weight and volume are at a premium, and an increase in pyrotechnic system weight and volume presents packaging and weight management problems which may require significant engineering time to solve.
One source of these problems is cable size and weight. FIG. 1 shows a typical prior art installation of pyrotechnic initiators 100, where each pyrotechnic initiator 100 is connected to a fire control unit 102, which transmits firing energy to the pyrotechnic devices 100 when a signal to do so is received from a controller 104. Typically, these devices are connected in an inefficient branching configuration. That is, a separate cable 106 connects each pyrotechnic device 100 individually to a fire control unit 102. Each of the cables 106 is a high-power cable, shielded to reduce or eliminate exposure to electromagnetic interference (EMI), electromagnetic pulse (EMP), or radio frequency (RF) interference within the cable 106. If the cable were not shielded, these sources of interference could potentially interfere with the operation of one or more of the pyrotechnic devices 100. The cables 106 used are typically at least as large as 18 gauge, because the cables 106 typically have to carry large transient currents of one to five amperes or more during firing. In the aggregate, the large number of high-power shielded cables 106 required for the branching configuration of the prior art are heavy and occupy significant volume, resulting in weight and packaging difficulties within an aircraft, spacecraft, missile, launch vehicle or other application where weight and space are at a premium. Further, in current systems, each fire control unit 102 can typically only support a relatively small number of pyrotechnic devices 100. Thus, multiple fire control units 102 may be required, further increasing the weight and volume of the overall pyrotechnic system 108.
Pyrotechnic systems used in aerospace systems also typically require a separate ordnance system battery 112 and power circuit, independent from the vehicle avionics batteries 110. This separate power system is required because surge currents occur in the power cabling when a pyrotechnic device is fired, potentially interfering with the avionics system. One or more separate ordnance system batteries 112 typically are used for firing. Due to the high delivery current required, the ordnance system batteries 112 are typically large and heavy. Thus, a separate ordnance system battery 112 and its attendant cabling add still more weight to a complex pyrotechnic system in an aerospace vehicle.